Pigmented oil composition and process of inhibiting oxidation thereof



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to c. m: NEMOUBS a we D1, 01 NE'WBURGH, NEW YORK, ASSIGNOR T E. I. DU PQN'I DE OF WILMINGTON, DELAWE, A CORPORATION OF DELA- PIGTED OIL COMPOSITION AND PROCESS OF INEIBITING OXIDATION TRUE No Drawing.

This invention relates to compositions. at least one constituent of which is an organic material, for instance, a liquid such as an unsaturated fatty oil, which has a tendency to undergo a chemical change at ordinary room temperature C.) when exposed to air and to actinic light; of which another constituent is a pigment; and of which another constituent is a material functioning to prevent or inhibit said chemical change of the first mentioned constituent. My invention also includes the process of inhibiting the oxidation in the presence of air of an organic material of the kind first above i mentioned, and having present therewith a pigment, by dispersing, at least throughout the surface portion of such material, a material functioning to prevent or inhibit said oxidation.

One important feature of my'invention is the retarding of the development of rancidit v of oils which tend to become rancid u exposed to air, in those cases where a w pigment is used with the oil, the inven 3 providing for this retardation without (1 eterious effect on the pigment, or the introduction of other objectionable features. One of the chief objects of my invention, from the aspect just indicated, is to improve upon white or light colored nitrocellulose dope compositions for use in coating of fabrics, paper, split leathers, and in general for leather substitute uses;

It has been customary to use vegetable oils 5 as softeners for pyrox lin compositions;

castor' oil is very generally used in the surface film of artificial leather; and either castor oil or blown rapeseed oil is used in most of the dope applied to split leather. It is noteworthy that the oils used for this purpose belong for the most part in the class of unsaturated glycerides. It is well known that unsaturated fatty oils, as, for example, castor oil, upon exposure to air, deveiop a ran- Application filed March 21, 1924. fierial No. 700,817..

rancidity development is especially marked where the oii is afloonstituent of a coating composition for, in this case, because of the extensive exposed surface, the action of oxygen on the oil is facilitated. The addition of various substances to oils for the purpose of preventing rancidity therein was proposed many years ago. The present invention relates to a particular phase of this general problem of preventing oxidation and pigment; or compositions aving a white or as light colored pigment the problem is diflicult. Various preventives of oxidation of oils, sailed anti-oxidants, have been tried, but they had various objectionable features. Some,

for example beta-naphthol, cause yellowing 7 after the product is exposed to light; some cause initial discoloration, which is too much for correction by pigment; some cause a setting of the pigmented pyroxylin 'elly; some cause the evolution of organic sulp ide fumes sufiicient to produce an objectionable odor, as when tartaric acid is used with hthopone white pigment; some cause the preservative to be ineffective as is the case when using citric acid with zinc oxide; the used tartaric acid with zinc oxide is not entirely satisfactory; zincoxide is an accelerator of oxidation of the oil; and so on.

fiiow, according to my invention, I use a white pigment which 1s less accelerative,

that is, is less active in promoting oxidation of "is oil, than is zinc oxide; and with this less aecelerative pigment I use an hydroxypo basic acid which will not cause evolution raven-ting 60 is oid odor which is quite objectionable. This of fumes suificient to produce an objectionable odor. I have found particularly desirable lithopone and citric acid in combination; Not only is lithopone less accelerative than is zinc oxide, and therefore, satisfactory from that viewpoint, but also it, as distinguished from zinc oxide, does not cause the citric acid to be inefiectivethe-acid, despite the. lithopone, exerts a strong preservative influence on the oil. Also, by using citric acid with lithopone, the production of objectionable odors, produced by the combination, tartaric acid and lithopone, is avoided. Again, there is no causing of a setting of the pigmented jelly. The addition of even a small quantity of citric acid, as one per cent of the weight of the oil, efi'ects a marked decrease in the rate of rancidity development under conditions which are normally favorable to such a change.

The above discoveryis particularly useful in preserving the freshness of the oil in white or light colored coating compositions where, forv example, nitrocellulose, an oil, generally castor oil, pi ment and rancidity retarder'are incorporate by a suitable volatile solvent and spread on a cloth backing. The previous conditions militating against the addition of a rancidity retarder to coating compositions containing white or, light colored pigment aving been overcome, fabrics coated with a composition containing such a pigment may be produced in which the deterioration of the coating composition is guarded against, and

the retention of the original pliability of the film ensured.

As a specific example of working in accordance with the invention, but not as a limitation, I give the following: Prepare a coating jelly as follows: Dissolve twelve ounds of pyroxylin in eight -eight pounds 0 a mixture of equal arts 0 ethyl alcohol and ethyl acetate and t en add twelve ounds of castor oil, thirt pounds of a mixture of lith0-. pone groun with castor oil in the proportionv of two parts of pigment, one part 0 oil and .44 pound of'dry citric acid, i. e. two per cent based on the total oil. This Kelly is applied to white cloth in an of t e various ways commonly known to t e fabric coating art for the production of artificial leather. The proportions of pyroxylin and solvent may, of course, be varied considerably depending on the character of the nitrocellulose, it being customary to use between eight and twenty pounds of pyroxylin for one hundred pounds of solution. The relation of the oil to the yroxylin depends on the pliability desired, t e example given giving a very pliable film. It is desirable to base i the amountof preservative upon the amount of citric acid it is to be understood that the invention includes the use of esters of citric acid and such salts as are soluble in the solvent mixture. For convenience in claiming I have referred to compound containing the citric acid radical, meaning by citric acid and including compounds in which one or more of the hydrogen atoms of the COOH groups has been replaced to form a salt or ester. Also while I have more particularl mentioned citric acid it is to be unders that other acids fulfilling the desired objects of the invention, as malic may be used. Also other pigments than lithopone, less accelerative thanzinc oxide, as titanium oxide, may be used.

I claim:

l. A coating composition comprising accllulose compound, a fatty oil having a tendency to become rancid, a pigment of the group composed of lithopone and titanium oxide, and a compound containing the radical of an acid of the group composed of citric and malic acids.

2. A coating composition comprising nitrocellulose, a fatty become rancid, a pigment of the grou composed of lithopone and titanium oxidz, and a compound containing the radical of an acid of the group composed of citric and malic acids.

3. A coating com 'osition comprising'nitrocellulose, a fatty oi having a tendency to become rancid, a pigmentof the grou composed of lithopone and .titanium oxi e, and an acid of the group composed of citric and malic acids.

4. A coating composition comprising nitrooil. having a tendencyto a com ound conlithopone, and an acid 6. A coating composition comprising nitro- I cellulose, castor oil, lithopone, and citric acid between about 1 to 5 per cent by weight, based upon the amount of said oil.

7. A coating composition comprising nitrocellulose, a fatty oil having atendency to become rancid, titanium oxide, and a compound containing the radical of an acid of the group composed of citric and malic acids.

8. A coating composition comprising nitrm cellulose, castor oil, titanium oxide, and an group composed of citric and acid of the malic acids.

.9. A coating composition comprising nitromenace 3 cellulose, castor oil, titanium om'de and citric acid between about 1 to 5 per cent'hy weight, based upon the amount of said oil.

10. Process of retarding the development of rancidity in alight colored pigmented nitrocellulose film' containing a fatty oil having a tendency to become rancid and a white pigment which comprises using as the white pigment in the composition from which the film is formed, a pigment selected from the group composed of lithopone and titanium oxide, and adding to the composition as rancidity retardant for the oil a compound containing the radical of an acid of the group composed of citric and malic acids.

In testimony whereof I afiix my signature.

' JOHN C. EMHARDT.

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